Rates of heroin addiction are increasing worldwide with concomitant legal and health costs, including increased risk of HIV and hepatitis C viral transmission. However, at present it is difficult to impossible to study the consequences of "pure" heroin use since the majority of addicts are polysubstance-dependent. Further, co-morbid conditions, such as Antisocial Personality Disorder (APD) and psychopathy, additionally complicate the clinical picture and daily function of heroin-dependent persons. Study of the effect of drugs of abuse on the brain and the development of addiction are particularly difficult, due to difficulty in isolating drug effects on cognition from dysfunction associated with co-morbid conditions. We propose to develop a program of studies with the long-term goals of investigating neurocognitive aspects of brain function in drug addicts with and without a diagnosis of ASPD / psychopathy. This program will be developed in Bulgaria, a low-middle income country in Southeastern Europe with significantly high prevalence of heroin addiction. Bulgaria's geographical position make it a key country on the "Balkan Drug Route", one of the main routes for international drug traffic from South-West Asia to Western Europe, through which approximately 80% of the heroin currently used in Western Europe passes. Consequently, heroin is easily available in the country, and in fact heroin addiction has become one of the most significant health and legal problems. Patterns of heroin addiction in Bulgaria are unique in that polysubstance dependence is uncommon. Consequently study of Bulgarian addicts provides a unique opportunity to evaluate neurocognitive and psychiatric consequences of relatively "pure" heroin use. In addition, the nature of the Bulgarian legal system facilitates the opportunity to study heroin dependent subjects both with and without APD because all detainees arrested for drug-related charges undergo mandated medical and psychiatric evaluation prior to disposition of their cases. We have partnered with physicians and mental health professionals in Sofia who have access to a large population of pre-trial detainees, a large majority of whom have been detained for drug-related crimes. Research on addiction and its neuro-cognitive consequences is minimal in Bulgaria, despite a significant need to address these concerns. In the proposed project the PI, her colleagues the University of Illinois-Chicago, and at the Clinic of Forensic Psychiatry and Psychology at the State University Hospital of Neurology and Psychiatry in Sofia, Bulgaria, will initiate the development of resources for studies of neuro-cognitive function in heroin addicts with and without APD/psychopathy, and without polysubstance dependence. This preliminary work will culminate in a pilot study of neuro-cognition in heroin addicts with and without ASPD/psychopathy and an R01 application based on these pilot findings and other hypotheses developed in the course of the two years.